International patent application publication number WO 02/11093 AI discloses a theft deterrent system for mains powered appliances that incorporates a separate dedicated controller and one or more controlled appliances. The controller includes an automatic reset feature whereby, when left plugged in to the mains power supply, the controller will automatically transmit a reset signal to one or more appliances immediately after the mains power supply is restored to the controller following a mains power supply interruption. That is, operation of the reset feature occurs in the event of a mains power interruption and normal restoration thereof. For theft deterrence the appliance controller may include a motion sensing means and a battery which will prevent the automatic re-setting of the appliances should the controller be moved whilst the mains power is disconnected.
A problem with this known theft deterrent system is that it is of limited versatility because all theft or non-theft events upon which a consequential system action occurs are wholly dependent upon the controller, that is, the system primarily operates via control signals transmitted from the controller and received by the protected appliance(s) in a master-slave relationship. Thus, for example, the automatic reset feature, the context for operation of which is interpreted as a non-theft event, requires a power interruption to the controller but without disconnection of the controller from the mains. When there is disconnection of the controller from the mains, which is interpreted as a theft event, the automatic reset feature is disabled.
An object of the present invention is to provide a security system (or methods of operation, or program products) for not enabling, enabling or disabling electrical devices (for example, household appliances) of the system for deterring theft of such devices, which is more versatile than the above described known system. The present invention includes various aspects (see below), which generally include a feature that a bi-directional communication protocol is followed before an electrical device protected by the system either remains inoperable, or is enabled or disabled. Another object is to provide an embodiment wherein all the electrical devices of the system will be disabled upon the detection of an unauthorised event in respect of only one of those devices.
The discussion herein of the background to the invention is included to explain the context of the invention. This is not to be taken as an admission that any of the material referred to was known or part of the common general knowledge in Australia as at the priority date of any of the claims of the present application.